Method of manufacturing carbon-rich product and co-products

ABSTRACT

A method in which a parent hydrocarbon-rich material is processed so as to produce both a carbon-rich solid material that has a higher carbon to hydrogen ratio than that of the parent material and a carbon-deficient combustible gas that has a lower carbon to hydrogen ratio than the parent material. In the process, the material is activated by exposing it to a hot gas stream having elevated levels of one or both of carbon dioxide and water vapor. The combustible gas is combusted to produce heat. At least about 80% of the heat is used in one or more endothermic steps that include drying coal or biomass.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of PCT/US09/34356 titled“Method of Manufacturing Carbon-Rich Product and Co-Products” filed onFeb. 18, 2009, which itself claimed priority of the following threeprovisional patent applications: 61/066,247 filed Feb. 19, 2008;61/131,952 filed Jun. 14, 2008; 61/189,045 filed Aug. 16, 2008. Thisapplication also claims priority of provisional patent application Ser.No. 61/210,885 filed on Mar. 24, 2009. The disclosures of all of theseprior applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the production of acarbon-rich product (e.g. activated carbon) from a hydrocarbon materialsuch as coal and/or biomass with the generation of excess energy and thegeneration of a co-product which utilizes the excess energy for itsproduction.

BACKGROUND OF THE INVENTION

Many industrial processes require energy for one or more process steps.A typical energy demand is for material drying or water evaporation.Most industrial processes use natural gas or fuel oil for process heator steam production. Natural gas and fuel oil are premium fuels whoseprices fluctuate significantly and are also high-priced. Solid fuelssuch as coal are a low-cost alternate that can be used is several casesfor the same purpose. However, there are operational challenges withusing coal, either via combustion or gasification, because of theincreased carbon dioxide emissions relative to natural gas and alsobecause of the ash in the coal that causes operational problems such asdeposition and fouling of heat transfer surfaces. A new way of usingcoal for process heating applications or steam generation is required,which will minimize operational issues while at the same time minimizethe increase of the carbon footprint (carbon dioxide emissions).

Additionally, the use of solid fuel for energy generation, whileresulting in lower operating costs, requires equipment that is moreexpensive than when using clean fuels such as natural gas. When using asolid fuel, a higher return on capital investment is required via thesimultaneous generation of alternate products that carry a highereconomic value than just energy supply.

Several carbon-rich products have economic value and end-useapplications. These include but are not limited to the following:activated carbon and activated charcoal for various gas cleaning andliquid processing applications; carbon-rich solids that can be used forsoil amendment or as carriers of fertilizing compounds for slow-releaseinto the environment; ultra-high surface area carbons forultra-capacitors; and porous carbons for gas storage or gas separation.The activated carbon used for such applications is manufactured fromhydrocarbon materials like coal or coconut shells.

Manufacturing of these carbon-rich products is typically from ahydrocarbon source such as coal or biomass using the steps of pyrolysis(heating in a non-oxidizing environment) and/or further activation (suchas reaction with steam at high temperature to increase porosity orsurface area). For example, activated carbon with a surface area of 400m²/g or greater can be produced from lignite coal via the steps ofpyrolysis at 450 to 650° C. and reacting with steam at temperaturesbetween 750 and 1000° C. The production of such carbon-rich solids fromparent hydrocarbons results in a hydrogen-rich product gas (a mixture ofvarious compounds, in sum, having an elemental H/C ratio more than thatof the parent hydrocarbon) that is typically not fully utilized in themanufacturing of the carbon-rich solid. For example a very largefraction of the hydrogen-rich product gas in activated carbon productionis burnt and then quenched to reduce the flue gas to an adequatetemperature for the gas cleaning apparatus, cleaned, and then exhaustedinto the environment. Such operation is not efficient and results inemission of pollutants including carbon dioxide that are excessive.

In existing activated carbon production plants, a hydrocarbon materiallike coal or biomass is typically processed through the steps of (i)drying, (ii) carbonization, and (iii) steam activation (contacting withsteam at temperatures greater than about 800° C. to partially gasify thecarbonized material and increase its surface activity). These steps canbe performed separately, for example, in separate rotary kilns. They canalso be performed in one reactor such as a multiple hearth furnace.Instead of steam, carbon dioxide can also be used in the activationstep. Both the carbonization and activation steps generate combustiblegases (hydrogen-rich product gas). These gases are exhausted from theactivation carbon production furnace into a separate combustion chamberwhere they are oxidized with air to mainly carbon dioxide and watervapor before being sent to an air pollution control system to removepollutants such as sulfur dioxide and particulate. Steam for theactivation step is typically generated in the combustion chamber with aheat exchanger.

The combustible gases from the carbonization and activation stepstypically contain condensable tars, which are the product of coaldevolatilization. If there are locations in the process equipment thatare colder than the condensation temperature, the condensed tars cancause deposits and fouling of the process equipment. The tars willremain in the gaseous phase if the temperature is maintained above theircondensation point, which typically ranges between 300-650° F. For theabove reason, the combustible gases from the carbonization andactivation steps have to be maintained at relatively high temperatures,pressurized and transported using blowers which consume substantialenergy, and combusted in a burner/combustion chamber that needs to bephysically closely coupled to the carbonization and activation reactors.

Up to 1 pound of steam per pound of feed coal may be required for theactivation furnace or about 1000-1200 Btu per pound of feed. This onlyrepresents about one-fifth the energy in the combustible gases. Incurrent generation plants, the remainder of the energy is wasted,resulting in a combustible gas energy utilization of only about 20%. Forexample, the gases are cooled with a water quench before being directedto an air pollution control system. Greater than about 60 percent of theheat in the original starting material for the production of activatedcarbon is exhausted into the environment without beneficial use.

Alternatively, in US Patent Application Publication No. 20070254807, anelaborate and expensive steam-to-electricity system is added on toextract some of the energy from the combustible gas into a usefulproduct. The efficiency of conversion to electricity in such plants isonly about 25 percent of the energy in the combustible hot gases leavingthe activated carbon production process. Also a significant amount ofequipment and expense is required to set up the power plant, includingsteam production heat exchangers (boiler), steam turbines andcondensers. A major portion of the heat is exhausted to the environmentin the condenser section, where the low pressure steam is contacted withcooling water to condense it before its return to the boiler. Thecooling water is then cooled in a cooling tower and heat rejected to theenvironment before being returned to the condenser. The low energyutilization occurs because only the expansion energy associated with thehigh temperature, high pressure steam is used in a steam turbine and thelatent heat of evaporation associated with the water is rejected to theenvironment.

Yet another potential use for the combustible gases from the productionof activated carbon from coal or biomass is its conversion to liquidfuels or chemicals. However, the composition and purity (cleanliness)requirements for the conversion of the combustible gases from theactivated carbon production furnace to fuels and chemicals are verydemanding. A narrow range of molecular hydrogen (H₂) and carbon monoxide(CO) ratios are required. No diluents, such as nitrogen, can be used,requiring the use of pure oxygen in the generation of the combustiblegases. The gases also need to be treated and cleaned to remove manycontaminants such as sulfur compounds and ash to prevent poisoning ofcatalysts in downstream processing equipment before their conversion toliquid fuels or chemicals. The application to convert to liquid fuels orchemicals is therefore very expensive and requires extensive equipmentand many processing steps.

SUMMARY OF THE INVENTION

It is an object of this invention to use the low-CO₂ producing energycontent of the combustible gases from the activated carbon productionreactor in a simple and cost-effective manner.

A high efficiency (greater than about 50 percent) and low capital costsolution with effective energy utilization (low carbon dioxideemissions/unit of energy use) is a beneficial means of handling thecombustible off-gases from an activated carbon production furnace.

The present invention relates generally to the production of acarbon-rich product (e.g., activated carbon) from a hydrocarbon materialsuch as coal and/or biomass with the generation of excess energy and thegeneration of a co-product (by physically co-locating the manufacturingof the co-product with the carbon-rich product manufacturing) whichutilizes about 50% or more of the excess energy for its production. Theproducts that can be co-produced with the carbon-rich product include,but are not limited to, the following:

i) Paperboard from wood or recycled paper

ii) Wallboard from gypsum

iii) Cement clinker from limestone

iv) Ethanol from biomass or corn

v) Electricity and space heating and cooling

vi) Dried/upgraded coal or biomass from moisture-laden coal/biomass.

The combination of the production of the carbon-rich product (e.g.activated carbon), and the production of co-product(s) via energyconsuming processes, such as paperboard, gypsum wallboard, cementclinker, ethanol, space heating or coal and biomass drying, providessignificant reduction in CO₂ emissions, cost savings through requiringfewer pieces of equipment, reducing material inputs, improvingoperations and increasing efficiency.

Coal and/or biomass processed for the activated carbon plant produces acarbon-deficient (relative to the parent hydrocarbon) combustible gas,which can advantageously be used for process heat in the manufacturingof the co-product, thereby reducing equipment costs, material inputs,and pollutant and greenhouse gas (CO₂) emissions. Activated carbonproduct resulting from the activated carbon production portion of theinventive process may be used in any activated carbon applicationincluding, for example, to reduce heavy metal (e.g. mercury) emissionsand/or to control NOx emissions in power plant flue gas, for example,coal-fired power plant flue gas, by contacting the NOx-containing fluegas with activated carbon thereby converting NO to N₂.

One embodiment of the invention produces a carbon-rich product, such asactivated carbon, from a hydrocarbon material, such as coal or biomass,while simultaneously utilizing the energy content to greater than about50 percent efficiency of the carbon-deficient gases (a mixture ofvarious compounds, in sum, having an elemental C/H ratio less than thatof the parent hydrocarbon) released from the conversion of thehydrocarbon material to a carbon-rich product.

Another embodiment of the invention produces one or more products inaddition to the carbon-rich product, these additional products(“co-products”) requiring one or more endothermic (energy consuming)steps in their manufacturing process, the energy requirements for whichare supplied, at least in part, by the combustion of carbon-deficientgases released from the conversion of the hydrocarbon material to thecarbon-rich product. The manufacturing activity of the co-product isphysically co-located with manufacturing of the carbon-rich product touse the excess energy of the carbon-deficient combustible gases releasedfrom the manufacturing of the carbon-rich product.

Another embodiment of the invention reduces carbon dioxide emissionsresulting from the use hydrocarbons, such as coal and biomass, whilesupplying energy to the endothermic steps in the manufacturing of theco-products.

Another embodiment of the invention minimizes the impact of inorganicconstituents (ash) in hydrocarbon fuels, such as coal and biomass, oncombustion and heat exchange equipment operation, including ashagglomeration and ash deposition.

Another embodiment of the invention utilizes moisture-rich or carbondioxide-rich gases released during the manufacturing of the co-products(e.g. in a drying step) as an activating gas in the production of thecarbon-rich product from the hydrocarbon material.

Another embodiment of the invention utilizes waste hydrocarbon materialgenerated in the manufacturing of the co-products as a raw material inthe reactor for the production of the carbon-rich product.

Another embodiment of the invention utilizes partially processedhydrocarbon material generated in the manufacturing of the co-productsas a raw material in the reactor for the production of the carbon-richproduct.

Another embodiment of the invention contacts the carbon-deficient gasesfrom the carbonization and activation steps with the “dried” andupgraded coal or biomass or the wet coal/biomass or a combination of the“dried” and wet coal/biomass to condense the tars. The amount of “dried”and or wet coal/biomass relative to the amount of tar is adjusted tomaintain a dry flowable product (i.e., tar/coal ratio is kept below avalue where the combined material does not becomes sticky) The thermalenergy in the carbon-deficient gases can be used advantageously dry aportion of the wet coal/biomass while simultaneously the coal/biomass bea site for tar condensation and solidification.

The invention comprises a method and system for co-producing a product(such as gypsum wallboard, paperboard, ethanol or “dried” and upgradedcoal or biomass) in an energy consuming process (such as drying) and acarbon-rich product (such as activated carbon) from a hydrocarbonmaterial such as coal or biomass.

In this method, carbon-rich product, such as activated carbon, isproduced by carbonizing a hydrocarbon material to yield a carbonizedproduct and carbonization product gases; activating the carbonizedproduct with steam or carbon dioxide to yield activated carbon andactivation product gases; such that the combination of the carbonizationproduct gases and the activation product gases have a lowercarbon-to-hydrogen (C/H) ratio compared to the parent hydrocarbonmaterial. These carbon-deficient combustible gases are combusted togenerate excess energy for use in the manufacture of co-products, whichrequire this input of energy in one or more steps of their production.The use of the carbon-deficient combustible gas as the energy sourceminimizes the emission of CO₂ into the environment compared to completeconversion and utilization of the coal or biomass, either through directcombustion or through complete gasification followed by combustion ofthe gasification products. Also, by only partially converting the carboncontent of the parent material, and not releasing the included ash andother inorganic constituents in the carbon material to interact witheach other, issues related to deposition on heat transfer surfaces andagglomeration are minimized or eliminated during the energy generationstep of combustion of these carbon-deficient gases.

The parent hydrocarbon material can be coal, peat, lignite, bituminouscoal, sub-bituminous coal, anthracite, petroleum coke, wood, biomass, orother hydrocarbon waste material such as recycled paper. The parenthydrocarbon material to be used in the invention can also have waterassociated with it, such as waste paper sludge.

In one of the embodiments, the parent hydrocarbon material in thisinvention for the co-product is preferably a moisture-laden materialthat would benefit from moisture removal and upgrading to a higherenergy density material. Preferred parent hydrocarbon materials arepeat, lignite, sub-bituminous coals, wood, biomass, or other hydrocarbonwaste material such as recycled paper or waste paper sludge.

The carbonization and activation product gases (comprising predominantlycarbon-deficient combustible gases) from the carbon-rich productmanufacturing process, which have no useful application for any energyconsuming steps in the carbon-rich product manufacturing process, arecombusted in a burner (or multiple burners) and the sensible andchemical energy in these gases is converted into thermal energy for usein the various steps of the manufacturing of the co-product. Thisco-product can be, for example, paperboard, gypsum wallboard, ethanol,cement, electricity or space heating.

For example, the hot combustion gases generated in the above step can beused to contact wet materials for drying or for other processes thatrequire heat (endothermic process). Alternatively, or in addition, thecarbon-deficient combustible gases can be directed to a boiler (steamgenerating unit), where the sensible and chemical energy in thecombustible product gases from the activated carbon production isconverted by reacting with air (combustion), and the hot gases generatedfrom combustion used to make steam at a temperature and pressure thatwould be adequate for utilization in the energy consuming steps ofco-product manufacturing. Alternatively, or in addition, combustiblegases can be directed to a furnace [e.g., heat transfer fluid (oil)heating unit)] where the sensible and chemical energy in the productgases from the activated carbon production is converted to heating a“non-contact heat transfer fluid” that would be adequate for utilizationin the energy consuming steps of co-product manufacturing.

In all of the above cases, the flue gas generated from the combustion ofactivated carbon reactor product gases has a lower CO₂ content per unitof heat generated than direct combustion of the feed coal or biomass.

The inventive method and system of the combined production ofcarbon-rich high surface area product, such as activated carbon, whichgenerates net excess energy, and a co-product, which requires a netenergy input in its manufacturing process is described in severalpreferred embodiments below.

This invention features a method comprising providing a parenthydrocarbon-rich material, processing the parent material so as toproduce both a carbon-rich solid material that has a higher carbon tohydrogen ratio that that of the parent material and a carbon-deficientcombustible gas that has a lower carbon to hydrogen ration than theparent material, the process comprising activating the material byexposing it to a hot gas stream comprising elevated levels of one orboth of carbon dioxide and water vapor, combusting the combustible gasto produce heat, and using at least about 50% of the energy content ofthe combustible gas in a separate but physically proximate processcomprising at least one endothermic step. The carbon-rich solid materialmay be activated carbon with surface area of at least about 200 m²/gm,and more preferably at least about 400 m²/gm.

The endothermic step may include generating electricity. The electricitymay be generated by using the heat to produce steam that is used todrive a turbine. The method may further include using the steam leavingthe turbine in a heating or drying step in the separate but physicallyproximate process, thereby using at least about 70% of the energycontent of the combustible gas. The electricity may be generated by agas engine or other device, and the hot exhaust from such a device isused to generate steam that is used in the separate but physicallyproximate process.

The endothermic step may be a step of a separate but physicallyproximate process selected from the group of separate processesincluding ethanol production, paperboard production, gypsum wallboardproduction, moisture-laden coal and biomass drying and cementproduction. The method may further include adding supplemental fuel tothe combustible gas before the combusting step, to more closely meet thethermal needs of the separate but physically proximate process. Theendothermic step may involve water evaporation or drying, materialheating, or calcinations. The method may further include using the heatproduced from combustion in a separate process comprising at least oneendothermic step, the separate process resulting in part in a gas streamcomprising elevated levels of one or both of carbon dioxide and watervapor, and then using the gas stream at least in part as either the hotgas stream for activation of the carbon-rich solid material, or to coolthe carbon-rich solid material.

The separate but physically proximate process may include ethanolproduction. The heat from combustion may be used to generate steam thatis used in one or more endothermic steps of the ethanol production. Themethod may further include adding supplemental fuel to the combustiblegas before the combusting step. The ethanol production may result in theemission of volatile organic compounds (VOCs), wherein the at least someof the VOCs are used as a supplemental fuel. The ethanol production mayresult in the emission of volatile organic compounds (VOCs), wherein theat least some of the VOCs are combusted to produce heat used in the stepof processing the parent material so as to produce both a carbon-richsolid material that has a higher carbon to hydrogen ratio that that ofthe parent material and a carbon-deficient combustible gas that has alower carbon to hydrogen ratio than the parent material.

In an example of the inventive method, 9580 lb/h of activated carbon isproduced from 46,684 lb/h of lignite coal. The carbon-deficientcombustible gases generated in the activated carbon production areseparately combusted to generate 163,250 lb/h of steam required for aco-located production of 5820 gallons/h of ethanol. The CO₂ emissionfrom the two separate but co-located processes is 35,510 lb/h. The CO₂emissions from the inventive method are significantly lower than thecase where the parent hydrocarbon is used as fuel. For the same quantityof steam generation and ethanol production as the above case, 40,700lb/h of CO₂ emissions are generated by using the parent hydrocarbon.Even more remarkably, the individual production of activated carbon(9580 lb/h) and ethanol (5820 gallons/h) would generate a total of 76,210 lb/h of CO₂. The inventive method provides a greater than 50 percentreduction in CO₂ emission in the production of valuable productscompared to current manufacturing methods.

The separate but physically proximate process may include paperboardproduction. The heat of combustion may be used to generate hot gas orsteam that is used to dry the paperboard. The method may include addingsupplemental fuel to the combustible gas before the combusting step, togenerate sufficient steam for paperboard production. The parent materialmay include cellulosic waste from the paperboard production.

The separate but physically proximate process may include gypsumwallboard production. The method may further include adding supplementalfuel to the combustible gas before the combusting step.

The separate but physically proximate process may include cementproduction. The method may include adding supplemental fuel to thecombustible gas before the combusting step.

The separate but physically proximate process may include the drying ofadditional quantities of parent hydrocarbon material to generate a dryand higher energy density co-product which is the modified hydrocarbonwith lower moisture content. The heat from combustion may be used togenerate steam that is used in one or more of the drying and heatingsteps. The method may further include adding supplemental fuel to thecombustible gas before the combusting step. The drying of the wet parenthydrocarbon may result in the emission of volatile organic compounds(VOCs), wherein the at least some of the VOCs are used as a supplementalfuel. The drying may result in the emission of volatile organiccompounds (VOCs), wherein the at least some of the VOCs are combusted toproduce heat used in the step of processing the parent material so as toproduce both a carbon-rich solid material that has a higher carbon tohydrogen ratio that that of the parent material and a carbon-deficientcombustible gas that has a lower carbon to hydrogen ration than theparent material.

In an example of the inventive method, 1025 kg/h of activated carbon isproduced from 5,000 lb/h of lignite coal. The carbon-deficientcombustible gases generated in the activated carbon production areseparately combusted to generate hot gases used to dry 51,000 kg/h ofwet coal to 36,345 kg/h of “dry” coal product. The CO₂ emission relatedto the combustion of the combustible gases is 3,803 kg/h for theproduction of both the activated carbon and “dry” coal product. Thiscompares to CO₂ emission of 3,867 kg/h if the parent hydrocarbon hadbeen used as the fuel for generating the hot gases to dry themoisture-laden coal, which is higher than that for the inventive method.Even more remarkably, the individual production of activated carbon(1,025 kg/h) and “dried” coal (36,345 kg/h) would generate a total of7,670 kg/h of CO₂. The inventive method provides a greater than 50percent reduction in CO₂ emission in the production of valuable productscompared to current manufacturing methods.

The invention also features a method comprising providing a parenthydrocarbon-rich material, processing the parent material so as toproduce both a carbon-rich solid material that has a higher carbon tohydrogen ratio than that of the parent material and a carbon-deficientcombustible gas that has a lower carbon to hydrogen ration than theparent material, the process comprising activating the material byexposing it to a hot gas stream comprising elevated levels of watervapor, combusting the combustible gas to produce heat, using the heatproduced from combustion in a separate process comprising at least oneendothermic step, the separate process resulting in part in a gas streamcomprising elevated levels of water vapor, and using the gas stream atleast in part as either the hot gas stream for activation of thecarbon-rich solid material, or to cool the carbon-rich solid material.This process preferably utilizes at least about 50% of the energy of thecombusted carbon-deficient gas.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features and advantages of the present invention willbecome fully appreciated as the invention becomes better understood whenconsidered in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic flow diagram of an integrated activated carbon andethanol production plant according to the invention;

FIG. 2 is a schematic flow diagram of an integrated activated carbon andpaperboard production plant according to the invention;

FIG. 3 is a schematic flow diagram of an integrated activated carbon andpaperboard production plant with waste paper utilization according tothe invention;

FIG. 4 is a schematic flow diagram of an integrated activated carbon andgypsum wallboard production plant according to the invention;

FIG. 5 is a schematic flow diagram of an integrated activated carbon andgypsum wallboard production plant that uses energy for gypsum dryingaccording to the invention;

FIG. 6 is a schematic flow diagram of an integrated activated carbon andgypsum wallboard production plant that uses energy for gypsumcalcination according to the invention;

FIG. 7 is a schematic flow diagram of an integrated activated carbon andcement production plant according to the invention;

FIG. 8 is a schematic flow diagram of an integrated activated carbon anddried upgraded coal production plant according to the invention;

FIG. 9 is a schematic flow diagram of a process for the co-production ofactivated carbon and upgraded “dried” coal using thermal drying of theraw coal according to the invention;

FIG. 10 is a schematic flow diagram of a process for the co-productionof activated carbon and upgraded “dried” coal using compaction followedby drying of the raw coal according to the invention; and

FIG. 11 is a schematic flow diagram of a process for the co-productionof activated carbon and upgraded “dried” coal using thermal drying withhigh-moisture gas recycle to the activated carbon furnace according tothe invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

This invention may be accomplished in a method and system forco-producing a product (such as gypsum wallboard, paperboard or ethanol)in an energy consuming process and a carbon-rich product (such asactivated carbon) from a hydrocarbon material such as coal or biomass.This is performed by directing the hydrogen-rich combustible gases fromthe activated carbon production reactor and using its energy content bycombusting it and using the released energy to a high efficiency in theenergy consuming steps of manufacturing of the co-product.

The preferred embodiments are described below.

I. Activated Carbon and Ethanol Co-Production

Activated Carbon Production from Hydrocarbon Feedstock and Production ofLower C/H Ratio Hot Combustible Product Gas than Parent Feedstock

In this method (FIG. 1) activated carbon and ethanol are produced inco-production plant (10). Activated carbon is produced in the activatedcarbon manufacturing plant section (20) by carbonizing a solid orpartially solid (e.g. wet) carbonaceous material to yield a carbonizedproduct and carbonization product gases; activating the carbonizedproduct with steam or carbon dioxide to yield activated carbon andactivation product gases; such that the combination of the carbonizationproduct gases and the activation product gases (hydrogen-rich hotcombustible product gases from the activated carbon reactor) have alower carbon-to-hydrogen (C/H) ratio compared to the parent carbonaceousmaterial. In the above method carbonizing or pyrolysis is typicallyperformed at 400 to 600° C. and activation with steam is performed at700 to 1000° C.

Activated carbon produced by the above method has a surface area of atleast 200 m²/gm, preferably at least, 350 m²/gm, and more preferably atleast 500 m²/gm. Surface areas are determined by theBrunauer-Emmett-Teller N₂ adsorption method.

A multiple hearth furnace (MHF) may be used as the activated carbonproduction reactor (26). Coal or other carbonaceous feedstock isprepared via hammer mills (24) to about ⅛″ to ½″ in size and introducedto the top of the activated carbon production reactor. The carbonaceousmaterial goes through a series of steps including drying,devolatilization and activation in the MHF to product activated carbon.The hot gases leaving the activated carbon production reactor containfine particulate. The fine particulate, which is partially processedmaterial, is collected in a cyclone (28) and advantageously returned tothe reactor for further processing.

Chemical activation of the carbonaceous feedstock instead of physicalactivation may also be used. In chemical activation, the carbonaceousmaterial is mixed with a dehydrating agent such as zinc chloride,phosphoric acid or alkali hydroxide such as potassium hydroxide. This isfollowed by heat treatment to temperatures between 450 and 900° C. tocarbonize the material and release hot combustible product gases.

In this first embodiment, the co-product manufactured through one ormore energy consuming steps is ethanol. In the ethanol manufacturingsection (50) of the process (FIG. 1), corn or other high-starch grains(or other biomass used in ethanol production) is first ground into mealand then slurried with water to form a mash. Enzymes are added to themash to convert the starch to the simple sugar, dextrose. Ammonia isalso added for pH control and as a nutrient to the yeast. The mash isprocessed in a reactor (52) through a high temperature cook step, whichreduces bacteria levels prior to fermentation. Steam is used for thehigh temperature cooking step.

The mash is then cooled and transferred to fermentation vessels whereyeast is added and the conversion of sugar to ethanol and carbon dioxide(CO₂) begins.

After fermentation, the resulting “beer” is transferred to distillationwhere the ethanol is separated from the residual “stillage”. The ethanolis concentrated to 190 “proof” using conventional distillation in thedistillation column (54). Steam is used for the distillation step.

The residual “stillage” from distillation is separated into a coarsegrain fraction and a “soluble” fraction by centrifugation in thecentrifuge (56). The soluble fraction is concentrated to about 30%solids by evaporation in the evaporator (58). This intermediate iscalled Condensed Distillers Solubles (CDS) or “syrup.” Steam is used forthe evaporation process.

The coarse grain and syrup fractions are then mixed and dried to producedistillers dried grain and solubles (DDGS), a high protein animal feedproduct in the dryer (60). Steam is used for drying step.

As described above, the production of ethanol from corn requires energy,in the form of steam, for various processing steps—about 10% in thecooking process, 30% in the ethanol evaporation, 15% in ethanoldistillation and 45% for drying the distiller grains. About35,000-40,000 Btu of process heat per gallon of ethanol is required. Forexample, a 50 million pound per year ethanol production plant will useabout 1,540 million pounds of steam per year (steam at 365° F., 150psig). This translates to about 180,000 lbs/hr of steam.

Ethanol may be manufactured by other energy consuming methods such ashydrolysis or gasification and with starting materials such ascellulose. These processes also require energy in their varioustransformation steps, and this invention covers these methods as well.

Production of Steam for the Ethanol Manufacturing Plant from theCombustion of Hot Combustible Product Gas from the Activated CarbonProduction Plant

In this embodiment of the inventive process, activated carbon andethanol are co-produced in a plant (FIG. 1), and at least a portion ofthe steam (process heat) required for the ethanol section of the plantis produced through the combustion of hydrogen-rich combustible gasgenerated in the activated carbon production reactor. Thecombustor/boiler (32) is one known in the art and typically comprises aburner, combustion chamber and heat transfer coils. The heat generatedfrom the combustion process is transferred to water entering the heattransfer coils. Water is converted to a pressurized and hot steam flowthat can be advantageously used in the various endothermic steps ofethanol manufacturing.

Cooling of Hot Activated Carbon Product with CO₂-Rich or Moisture-RichEases from Ethanol Plant

Activated carbon leaving the bottom of the activated carbon productionreactor, such as a MHF is at a high temperature, typically around 1500to 1700° F. This hot material is typically cooled with an indirect heatexchanger before being discharged. In an embodiment of the invention,the hot activated carbon product is advantageously cooled withmoisture-rich gas stream or CO₂-rich gas stream from the ethanol plantin a heat exchanger (not shown). The heat exchanger can be of anindirect contact type, or a direct contact heat exchanger. If directcontact heat exchange is used, the gas streams should have a maximum ofabout 1 percent O₂, preferably less than 0.5% O₂ to prevent oxidationand degradation of the activated carbon product. The heat exchanger ispreferably operated in a predominantly counter-current mode, with thehot activated carbon product and the “cooling” gas streams flowing in acounter-current fashion. The heated (moisture-rich or CO₂-rich) gasstream can then be advantageously used subsequently as process gas inthe activation step of the activated carbon plant.

Use of Moisture-Rich or CO₂-Rich Exhaust Gases from the EthanolManufacturing Plant as Process Feed Gas for Activation in the ActivatedCarbon Production Reactor

In another embodiment of the combined activated carbon and ethanolplant, at least a portion of several exhaust gas streams in the ethanolmanufacturing section plant that are almost pure steam (moisture) or CO₂are used as activation process gas. For example, if an indirectsteam-driven dryer is used for the production of DDGS, the exhaust gasesfrom the dryer (from the drying process) are almost completely purewater vapor. The gases leaving the fermentation section of the ethanolmanufacturing section of the plant are almost completely pure CO₂. Thesestreams may be advantageously used as process gas for the activationstep in the activated carbon plant. These gas streams may beadvantageously preheated as described in the preceding paragraphs beforeintroduction into the activation section of the activated carbon plant.By using the moisture-rich stream from the ethanol plant in theactivated carbon plant, water and energy consumption for the combinedplant is reduced, since steam required for the activation step in theactivated carbon plant does not have be raised separately.

The flue gas from the combustion of the hydrogen-rich combustible gasproduced by the activated carbon reactor is treated to reduce theconcentration of various pollutants in a manner that is known in theart. For example, ammonia can be injected in the flue gases at atemperature of about 1500-1800° F. to reduce the nitrogen oxides tomolecular nitrogen. Alkaline material, such as lime slurry can beinjected into the flue gas to capture sulfur oxides, and the coal ashand scrubber particulate can be removed using a dust collector such as afabric filter.

Co-Firing of Coal and Hot Combustible Product Gas from the ActivatedCarbon Production Plant for Steam Production for Ethanol Manufacturing

In an alternate embodiment, if the ethanol section of the plant requiresmore energy than what is provided by the combustion of the hydrogen-richcombustible gas from the activated carbon reactor, supplemental firingof additional fuel may be used. This additional fuel can be coal,preferably, or an alternate fuel, such as natural gas.

The hydrogen-rich combustible gas from the activated carbon productionreactor may be fired simultaneously with the supplemental fuel in anadvantageous manner to reduce pollutant emissions such nitrogen oxides.For example, the hydrogen-rich combustible gas may be preferentiallyintroduced in a reducing zone of the combustor, followed by stagedaddition of combustion air into the combustor to minimize nitrogen oxideformation and complete combustion. Alternately, the combustible productgas can be introduced into the combustor as a “re-burn” fuel at adownstream location of the combustor to reduce nitrogen oxides formedupstream in the combustor.

Boosting Pressure of the Hot Combustible Product Gas from the ActivatedCarbon Plant

Depending on the operation of the activated carbon reactor, thehydrogen-rich combustible gas from the reactor may need to be deliveredat a higher pressure to downstream components/devices than madeavailable at the exit of the reactor. A higher pressure may be required,for example, to obtain better distribution of the combustible gas withina downstream device. In such cases, a fan (30) that can handle hot andparticulate-laden gas streams may be used. If the combustible gas fromthe activated carbon plant has too high a temperature for it to beeffectively handled by a fan, then it may be cooled down to thenecessary temperature before its introduction into the fan. Cooling maybe achieved with a heat exchanger, where additional steam can begenerated, or by mixing in a cold gas stream.

Handling of Water/Steam from and to the Boiler/Combustor

The boiler/combustor (32) that burns the combustible gas from theactivated carbon reactor has a water inlet and steam outlet. Boiler feedwater is compressed to a desired pressure and pumped through the boilertubes and extracts heat from the hot gases generated from the combustionof the combustible product gas with air. Steam temperature and pressuresare chosen to efficiently operate and satisfy the heat demand of thevarious ethanol manufacturing steps. Typical conditions for steam supplyto the ethanol plant are 150 psig pressure and 370° F. temperature.

In some of the production steps in the ethanol plant, steam is contacteddirectly with other materials. In other production steps such as thedrying and production of the DDGS, steam is used in an indirect mannerand does not contact other materials. In such cases, the condensed steam(after its useful energy has been transferred) is redirected to theboiler as boiler feed water. Additional (make-up) boiler feed water froma boiler feed water treatment plant is mixed with the returningcondensate and then sent to the combustor/boiler.

Destruction of Volatile Organic Compounds in Exhaust Streams fromEthanol Manufacturing in the Activated Carbon Production Plant or theCombustor/Boiler

Ethanol manufacturing uses various process steps and pieces of equipmentthat emit volatile organic compounds (VOC). VOCs may be emitted from thedryer, distillation columns, thermal oxidizer units, wet cake storagelocations, fermentation tanks, and other equipment associated withfermentation and distillation such as fluid bed coolers, coolingcyclones (62), and fermentation scrubbers. To prevent emission of VOCinto the environment, these streams may be advantageously routed to thecombustor/boiler (32). If these streams are oxygen-rich (i.e.predominantly air), they may be advantageously used as combustion airfor the combustor/boiler. In this manner, the high temperatures andoxidizing environment in the combustor/boiler can effectively destroythe VOC. To improve heat/process efficiency, these streams may be heatexchanged with the exhaust streams from the combustor/boiler (combustionair pre-heat), prior to being used as combustion air in thecombustor/boiler.

The VOC-laden air streams from the ethanol plant can also be used asprocess air and burner air in the activated carbon production reactor(26), although these quantities are expected to be much smaller thanthat required for the combustor/boiler.

The fermentation reactor in the ethanol manufacturing plant produces aCO₂-rich stream. This stream also has VOCs, which are typically removedwith a dedicated scrubber. In this embodiment of the inventiveco-production plant, the CO₂-rich stream with minor quantities of VOCcan be advantageously directed to the activation section of theactivated carbon plant and used as activation gas similar to steam. Inthis manner, a scrubber for the fermentation reactor may be avoided orused only when the activated carbon plant is not operating.

EXAMPLES Example 1 Ethanol and Activated Carbon Production Plant

An ethanol and activated carbon production plant with the identifiedimprovements (FIG. 1) and advantages relative to stand-alone plants isdescribed below. Coal (lignite) of the composition provided below isused as feed stock.

Composition wt-% C Carbon 34.6 H Hydrogen 3.5 S Sulfur 0.61 O Oxygen21.6 N Nitrogen 0.66 Ash 7.0 H₂O Moisture 32.0

Activated carbon yield from the activated carbon production reactor isabout 20-30 percent based on wet feed input. For a 46,684 lb/hour wetlignite input, this plant yields about 9,580 lb/hour (20% yield) ofactivated carbon product.

A typical activated carbon composition is shown below obtained fromprocessing the above-described feed stock in the proposed inventivemethod.

Composition wt-% C Carbon 68 H Hydrogen 0.5 S Sulfur 1.5 O Oxygen 0.5 NNitrogen 0.7 Ash 28.0 H₂O Moisture 1.0

Steam requirement for activation for the activated carbon productionplant is about 0.7 lb of steam per pound of wet feed. For a 46,684lb/hour wet lignite input, this translates to about 32,680 lb/hour ofsteam. This quantity of moisture-rich gas is almost completely availablefrom the ethanol DDGS dryer. For example, in the case shown theproduction amount of DDGS is 22 tons per hour, the corresponding amountof associated moisture would have been approximately 15 tons per hour or33,000 lbs/hour of water vapor. If additional steam is required, some ofthe steam generated in the combustor/boiler can be directed to theactivation zone of the activated carbon production reactor. In theexample discussed here, since the water vapor requirement for theactivation step is met almost completely by the dryer exhaust gases ofthe ethanol plant, no additional fuel firing is required to generatethis steam, unlike in a traditional activated carbon production plant.

The carbonization and activation product gases (comprised predominantlyof combustible gases) from the activated carbon production reactor arecombusted in a boiler (steam generating unit) where the sensible andchemical energy in the activated carbon reactor product gases isconverted to making steam at a temperature and pressure that is adequatefor utilization in an ethanol plant. The boiler as described abovecomprises a combustion zone, where activated carbon reactor gases arecombusted with air. To completely combust the hot combustible productgas from the activated carbon production reactor, in this example, about142,670 lb/hour of combustion air is required (corresponding to anexcess air of about 20 percent). This air stream is supplied from thevarious exhaust streams of the ethanol plant, which are predominantlycomposed of air with trace quantities of VOC. In this manner, a separateVOC destruction device is not required for the ethanol plant.

The steam produced (163,250 lb/hour) in the boiler from the combustionof the hot combustible product gases from the activated carbon reactoris advantageously directed to a corn-to-ethanol plant, where the steamis used as the energy source for various ethanol-manufacturing processsteps, including process heat, ethanol distillation, evaporation andconcentration of raw stillage, and drying of residual wet solids to drydistillers' grain solids (DDGS).

Alternatively, the steam produced in the boiler from the combustion ofthe hydrogen-rich combustible gases may also be directed to a power(back pressure) turbine to generate electricity, and exhaust steam fromthe turbine directed to the corn-to-ethanol plant section for processheat, including, for example, ethanol distillation and evaporation. Inthis case, the excess energy from the activated carbon production isused for both electricity production and process heat. Electricity mayalso be produced from the combustible gases directly in a gas engine andthe hot exhaust of the gas engine advantageously directed to generatesteam for the endothermic steps in the co-product (ethanol)manufacturing.

The flue gas generated from the combustion of activated carbon reactorproduct gases has a lower CO₂ content per unit of heat generated thandirect combustion of the feed coal or biomass. For example, in the aboveexample 35, 510 lbs/hour of CO₂ is generated for the required amount ofsteam for the ethanol plant operations, compared to 40,700 lbs/hour ofCO₂ with direct coal combustion in an ethanol plant (see comparativeexample below).

The energy content in the coal used is about 6400 Btu/lb and the totalenergy content coming into the process with the coal is 298 MMBtu/hr.The energy content leaving the process with the activated carbon isabout 96 MMBtu/hr. The remainder, excluding heat loss to theenvironment, is about 200 MMBtu/hr and is the energy content of thehydrogen-rich combustible gases. The energy used to evaporate the steam(163,250 lb/hr) is about 170 MMBtu/hr. The efficiency of energyutilization is about 85 percent.

The total amount of coal used for a integrated ethanol and activatedcarbon plant is 46,684 lb/hour to produce 163,250 lb/hour of steam(required for 5820 gallon per hour ethanol manufacturing plant) and 9580lb/hour of activated carbon product. In comparison, a separately locatedcoal-fired ethanol plant and a coal-fed activated carbon plant with fluegas quench would require a total of 78,180 lb/hour of coal. The totalCO₂ emissions from separately located plants would be 76,210 lb ofCO₂/hour compared to 35,510 lb of CO₂/hour for an integrated plant. Evenif the separate activated carbon production plant is equipped withrecovering the excess heat and converting it to electricity, theefficiency of conversion is only about 20 to 25 percent compared toabove about 80 percent for the integrated ethanol-activated carbonplant.

COMPARATIVE EXAMPLES Example 2 Separate Coal-Fired Boiler for EthanolManufacturing

A typical coal-fired boiler necessary for making steam to supply a 50million pound per year plant (5820 gallons of ethanol per hour) isestimated to be about 163,250 lb/hr of steam. Steam conditions are 150psig and 365° F. About 32,100 lb/hour of coal firing is required togenerate the above steam quantity. The coal considered in this case is alignite coal as described in the example with the integrated plant. Sucha boiler would need to be equipped with heat extraction in thecombustion section to keep flue gas temperatures at an operationallyacceptable level, if low quantities of excess air (<20 percent) are tobe used.

Combustion of the above indicated quantity of coal will generate about186,380 lb/hour of flue gas, if the excess air used is about 20 percentabove the stoichiometric requirement. Corresponding quantity of CO₂emissions in the flue gas is about 40,700 lbs/hour.

Alternatively, if a combustor without heat extraction in the combustionzone is to be employed, flue gas temperatures would need to be moderatedtypically by cooling with high amounts of excess air (˜300 percent). Anexample of this case would be to use 518,230 lb/hr of air with 36,439lbs/hour of coal to generate 555,000 lbs/hr of flue gas and 46,197lbs/hr of CO₂ and still only generate the above-identified quantity andquality of steam (163,250 lb/hr, 150 psig and 365° F.)

Example 3 Coal-Fired Activated Carbon Plant with Flue Gas Quench

An example of a typical coal-fired activated carbon production plant isprovided below. Lignite of the composition provided in the previousexample is used as feed stock. Activated carbon yield is about 20percent based on wet feed input. A portion of the heat generated fromthe combustion of the product gases from the reactor is used to generateprocess steam. Steam requirement for the activated carbon productionplant is about 0.7 lb of steam per pound of wet feed. For a 46,684lb/hour wet lignite input, this translates to about 32,680 lb/hour ofsteam. This plant yields about 9,580 lb/hour of activated carbonproduct. The remainder of the heat from the combustion of the productgas from the activated carbon production reactor has to be quenched witha water spray. About 133,380 lb/hour of water is required to quench theflue gases and achieve an outlet flue gas temperature of about 300° F.,which is optimum for operation of the pollution control equipment. Thisprocess yields an overall flue gas flow of 344,940 lb/hour (20 percentexcess air) and CO₂ emission of about 35,510 lb/hour, but the energy inthe hydrogen-rich combustible gases is not utilized.

Example 4 Coal-Fired Activated Carbon Plant with Heat Recovery for PowerGeneration

In a typical coal-fired activated carbon production plant flow diagramwith heat recovery for power generation, lignite of the compositionprovided in the previous examples is used as feed stock. Activatedcarbon yield is about 20 percent based on wet feed input. A portion ofthe heat generated from the combustion of the product gases from thereactor is used to generate process steam. Steam requirement for theactivated carbon production plant is about 0.7 lb of steam per pound ofwet feed. For a 46,684 lb/hour wet lignite input, this translates toabout 32,680 lb/hour of steam. This plant yields about 9,580 lb/hour ofactivated carbon product. The remainder of the heat from the combustionof the product gas from the activated carbon production reactor iscooled, while additional steam is generated. This steam is sent to asteam turbine for electricity production. About 10 MWe of electricitycan be expected to be produced, with a heat-to-electricity conversion ofabout 20-25%. This process yields an overall flue gas flow of 212,380lb/hour (20 percent excess air) and CO₂ emission of about 35,510lb/hour.

Electricity generation using a steam turbine by itself, typically onlyhas energy efficiency utilization between 20 and 35 percent, but for aplant of this size closer to 20 to 25 percent. The remainder of theenergy is lost to the environment during steam condensation in thecondenser, which is necessary to return water into a liquid state beforeit can be compressed and returned to the boiler.

II. Activated Carbon and Paperboard Co-production

In another preferred embodiment, (FIG. 2) activated carbon is producedin the activated carbon manufacturing plant section (20) of theactivated carbon and paperboard co-production plant (80) from thestarting hydrocarbon material such as coal or biomass in a similarfashion as outlined in previous embodiments and the co-productmanufactured through one or more energy consuming steps is paperboard.Energy for various endothermic steps of paperboard production issupplied from the excess energy that is generated from activated carbonproduction and which is associated with the hydrogen-rich combustiblegases generated therein.

FIG. 2 is one embodiment of the present disclosure of a system for anintegrated activated carbon and paperboard production process. FIG. 3 isanother embodiment of the present disclosure of a system for anintegrated activated carbon and paperboard production process with wastepaper utilization.

To form paperboard in the paperboard manufacturing section (90),recycled fiber mixed with water and other additives is discharged into aforming line. The “wet” board is then moved to dryer lines (92) whereexcess moisture is evaporated in a controlled manner. Energy for boarddrying is supplied by steam. Typically, a drum or a surface heated withsteam is contacted with the wet paper for the drying operation.Alternately, an air stream may be heated by the steam via a heatexchanger and the heated air stream supplied to the dryer to evaporatethe water.

Typically energy requirement for paperboard production is about 4-8MMBtu/ton.

Production of Process Heat for Paperboard Manufacturing Plant from theCombustion of Hot Combustible Product Gas from the Activated CarbonProduction Plant

In this embodiment, hot combustible gases generated from the pyrolysisand steam gasification of the solid or partially solid carbonaceousmaterial such as coal, carbonaceous waste from the paperboard plant, orother biomass is combusted with air in a boiler (32) to generate atleast some portion of the process heat/steam for the paperboardmanufacturing section of the plant. By using a potentially wasted fuel,the energy costs for the paperboard manufacturing are minimized andefficiency maximized.

In the paperboard making process, a significant amount of wet cellulosicwaste is generated during the initial screening process.

Utilization of Carbonaceous Residues/Waste from the Paperboard Plant inthe Activated Carbon Production Plant to Produce Activated Carbon andProcess Heat/Process Steam

In this embodiment (FIG. 3), the carbonaceous residues/waste from thepaperboard making steps can be advantageously fed to the activatedcarbon manufacturing section (20 a) at the top of the activated carbonmultiple hearth furnace (front of the activated carbon manufacturingprocess) along side other carbonaceous feed materials to produceactivated carbon and hot combustible product gases. Separate ordedicated equipment is not required for processing the residue/wastestream. Since the carbonaceous materials from the paperboard plant arerenewable (biomass-derived), the combustible gases generated from thepyrolysis and activation of the said material, their combustion andsubsequent heat extraction and utilization will result in less carbondioxide emissions resulting from the combustion of fossil-derived fuels.The paperboard is co-produced in the paperboard manufacturing section ofthe plant (90 a).

The emissions of pollutants including carbon dioxide can besignificantly reduced with the above invention because of theutilization of the waste energy from the carbon manufacturing section ofthe plant in paperboard manufacturing as well the use of wastecarbonaceous (“renewable”) materials in the paperboard section of theplant in the activated carbon manufacturing.

Co-Firing of Natural Gas and Hot Combustible Product Gas from theActivated Carbon Production Plant for Process Heat for PaperboardManufacturing

In an alternate embodiment, if the paperboard plant has larger heatrequirements than what can be provided by the hydrogen-rich gas from theactivated carbon reactor, then supplemental fuel, such as natural gas,may be advantageously co-fired or fired separately in the boiler.

Controlling Temperature of the Gases for Process Heat for PaperboardManufacturing

The temperature required for the drying and other operations may belimited by process considerations. Temperature of the hot product gasesgenerated from the combustion of the hydrogen-rich combustible gasesfrom the activated carbon reactor may be controlled by mixing “cold”recycled flue gas in a proportion to achieve the desired temperaturevalues.

Process Control for Paperboard Manufacturing

In another embodiment, natural gas is used in combination with thecombustible product gases from the activated carbon production reactorto enable control of the steam generated for paperboard production. Theproportion of natural gas can be minimized and set at values justnecessary for process control. Control of the quantity of steam asdefined by the requirements of the paperboard plant, is achieved bymonitoring the steam quantities generated from the combustible gasesfrom the activated carbon production reactor and supplementing it withnatural gas or oil firing. Process control is achieved by varying theamount of natural gas or oil firing and steam generation associated withthat firing.

Co-firing of natural gas and activated combustible product gas from theactivated carbon production reactor also enables “assured” processoperation or back-up fuel in case natural gas supply is interrupted orthe activated carbon production reactor has to be shut down.

Similar to the previous embodiment in the co-production of activatedcarbon and ethanol, the following advantageous aspects are included inthe preferred embodiments of co-production of activated carbon andpaperboard.

(i) Cooling of hot activated carbon product with moisture-rich gasesfrom paperboard manufacturing.

(ii) Use of moisture-rich exhaust gases from the paperboardmanufacturing as process feed gas for carbon activation in the activatedcarbon production reactor

EXAMPLES Example 5 Integrated Paperboard and Activated Carbon ProductionPlant

An integrated paperboard and activated carbon production plant with theidentified improvements (FIG. 2) and advantages relative to stand-aloneplants is described below. Lignite of the composition provided below isused as feed stock.

Composition wt-% C Carbon 34.6 H Hydrogen 3.5 S Sulfur 0.61 O Oxygen21.6 N Nitrogen 0.66 Ash 7.0 H₂O Moisture 32.0

The production of process heat for the paperboard production process isdescribed below. About 23,340 lb/hour of coal is introduced into amultiple hearth furnace. About 71,400 lb/hour air and 16,340 lb/hoursteam is introduced in the various hearths of the MHF and hot productgas combustor to generate the heat required and provide the optimumgaseous environment for the production of activated carbon as well ascombust all hydrocarbon and other combustible gases from the activatedcarbon production reactor. About 4,790 lb/hour of activated carbon isproduced from this reactor set-up. The hot combustible product gasesleaving the multiple hearth furnace (activated carbon productionreactor—ACPR) at the top is sent to a combustor/steam boiler. Air isadded to the burner to completely combust the hydrocarbons to yield hotflue gas, which transfers its heat via a heat exchanger to make productsteam (81,630 lb/hour, 370° F.). This steam is sent to the paperboardplant and used for paper drying and other process heating purposes. Inthe paperboard plant, the steam is condensed, transferring its heatmostly completely to the paper-making process. The loss of heat to theenvironment is mainly through equipment walls and in the flue gas (cleanexhaust) leaving the system.

Overall heat utilization efficiency of greater than 70 percent and morepreferably 80 percent of the chemical and sensible heat in the hotcombustible product gas from the activation carbon production reactor toboiler is achieved. The condensate obtained from steam condensation inthe papermaking process is returned to the boiler to be heated andevaporated again.

In the above set-up, about 17,760 lb of CO₂ is generated from coal and81,630 lb. of steam (at 370° F.) is generated via heat extractionresulting in 0.218 lb CO₂ per pound of steam generated. CO₂ emission foreach pound of steam generated by this method where activated carbon isproduced and the remainder (consisting of hydrogen-rich combustiblegases) is used for steam production (or heat utilization) is about 12.5percent lower than the comparative example of direct combustion of coalor combustion followed by complete gasification of coal, where all ofthe carbon content in the fuel is used for heating.

The energy content in the coal used is about 6400 Btu/lb and the totalenergy content coming into the process with the coal is 150 MMBtu/hr.The energy content leaving the process with the activated carbon isabout 49 MMBtu/hr. The remainder, excluding heat loss to theenvironment, is about 100 MMBtu/hr and is the energy content of thehydrogen-rich combustible gases. The energy used to evaporate the steam(81,630 lb/hr) is about 85 MMBtu/hr. The efficiency of energyutilization is 85 percent.

Example 6 Integrated Paperboard and Activated Carbon Production Plantwith Waste Paper Utilization

An integrated paperboard and activated carbon production plant with theidentified improvements with waste paper utilization (FIG. 3) andadvantages relative to stand-alone plants is described below.

Waste paperboard of the composition provided below is used as feedstock.

Composition wt-% C Carbon 26.0 H Hydrogen 3.5 O Oxygen 26.4 Ash 4.0 H₂OMoisture 40.0

Lignite of the composition provided below is also used as feed stock.

Composition wt-% C Carbon 34.6 H Hydrogen 3.5 S Sulfur 0.61 O Oxygen21.6 N Nitrogen 0.66 Ash 7.0 H₂O Moisture 32.0

The production of process heat for the paperboard production process andutilization of the waste paper sludge in the activated carbon productionprocess is described below. About 23,340 lb/hour of coal is introducedinto a multiple hearth furnace. About 6,600 lb/hour of waste papersludge (40% moisture) is also introduced to the top of the multiplehearth furnace. About 91,000 lb/hour air and 18,320 lb/hour steam areintroduced in the various hearths of the MHF and hot product gascombustor to generate the heat required and provide the optimum gaseousenvironment for the production of activated carbon as well as combustall hydrocarbon and other combustible gases from the activated carbonproduction reactor. About 5,100 lb/hour of activated carbon is producedfrom this reactor set-up. The yield of activated carbon based on thefeed coal is approximately 20 percent. The yield of activated carbonbased on the feed paper waste is approximately 5 percent. The hotcombustible product gases leaving the multiple hearth furnace (activatedcarbon production reactor) at the top is sent to a combustor/steamboiler. Air is added to the burner to completely combust thehydrocarbons to yield hot flue gas, which transfers its heat via a heatexchanger to make product steam (106,250 lb/hour at 375° F.). This steamis sent to the paperboard plant and used for paper drying and otherprocess heating purposes. In the paperboard plant, the steam iscondensed transferring its heat almost completely to the paper-makingprocess. The condensate is returned to the boiler to be heated andevaporated again.

In the above set-up, about 17,760 lb of CO₂ is generated from coal (noincrease compared to Example 5, since a renewable source, i.e. wastepaperboard, is used) and 106,250 lb of steam are generated resulting in0.167 lb CO₂ from coal per pound of steam generated. CO₂ emission foreach pound of steam generated by this method where a renewable sourcesuch as waste paper is used for a portion of the feed, activated carbonis produced, and the remainder (consisting of hydrogen-rich combustiblegases) is used for steam production (or heat utilization) is about 33percent lower than the comparative example of direct combustion of coalor combustion followed by complete gasification of coal, where all ofthe carbon content of the fuel is used for heating.

The energy content in the coal used is about 6400 Btu/lb and the totalenergy content coming into the process with the coal is 150 MMBtu/hr.The energy content of the waste paper is about 37 MMBtu/hr. The energycontent leaving the process with the activated carbon is about 52MMBtu/hr. The remainder, excluding heat loss to the environment, isabout 135 MMBtu/hr and is the energy content of the hydrogen-richcombustible gases. The energy used to evaporate the steam (106,245lb/hr) is about 110 MMBtu/hr. The efficiency of energy utilization isabout 82 percent.

III. Activated Carbon and Wallboard Co-Production

In another preferred embodiment, (FIG. 4) activated carbon and wallboardare co-produced in a plant (100). Activated carbon is produced from thestarting hydrocarbon material such as coal or biomass in a similarfashion as outlined in previous embodiments and the co-productmanufactured through one or more energy consuming steps is gypsumwallboard. Energy for various endothermic steps of wallboard productionis supplied from the excess energy that is generated from activatedcarbon production and which is associated with the hydrogen-richcombustible gases generated therein.

FIG. 4 is one embodiment of the present disclosure of a system for anintegrated activated carbon and wallboard production process plant.FIGS. 5 and 6 are detailed examples of this embodiment identifying theenergy sharing between the activated carbon production reactor and thegypsum drying and gypsum calcination steps of wallboard production.

In the wallboard manufacturing process, raw gypsum (synthetic or mined)is first dried, for example in a cage mill, using hot process gastypically obtained from natural gas firing. The dried gypsum (landplaster) is then calcined to form Plaster of Paris (CaSO₄.½H₂O) orstucco. The temperature of calcination is around 300 to 350° F.Calcination is performed in an impact mill, where hot gases, typicallyproduced from the combustion of natural gas, are contacted with thegypsum. Both size reduction and calcination are performed simultaneouslyto yield a fine calcined powder. Alternately, calcination can beperformed in a kettle calciner, where the heat is transferred to thegypsum particles indirectly. To form the wallboard, the stucco is thenmixed with water and other additives and discharged into a forming line.A portion of the water added to the slurry is consumed in formation andre-crystallization of gypsum in the wallboard. The “wet” board is thenmoved to dryer lines where the excess moisture is evaporated in acontrolled manner.

As described above, wallboard production requires heat for variousprocessing steps—up to 20% in the feed gypsum drying, another 25% ingypsum calcination, and about 55% in board drying. About 2 MMBtu/MSF(MSF=1000 ft²) of wallboard is required for the overall production.

Production of Process Heat for Wallboard Manufacturing Plant Section(110) from the Combustion of Hot Combustible Product Gas from theActivated Carbon Production Plant

In this combined activated carbon and wallboard co-production process(FIG. 4), at least a portion of the process heat required for thewallboard production is generated through the combustion ofhydrogen-rich combustible product gas that is generated in the activatedcarbon production reactor.

In one embodiment, a portion of the hot combustible product gas from theactivated carbon production reactor is directed to the burner (112) ofthe raw feed dryer. Combustion air is added to the burner to burn thefuel gases and generate a hot combusted product gas that can becontacted directly with the wet feed to evaporate the water and dry thegypsum material. The contacting of the hot gases and the wet gypsum canalso be performed in a rotary kiln dryer (120) or any other type ofdrying equipment. To modulate the temperature of the hot gasescontacting the wet gypsum, a recycle fan (126) may be used tore-circulate cold exhaust gases from the dryer (120 a) exit to the frontof the dryer or the burner (112 d) as shown in FIG. 5.

In addition to the above, another portion of the hot combustible productgas from the activated carbon production reactor can be directed to theburner (112 a) of the gypsum calciner (122) (FIG. 4). Combustion air isadded to the burner to burn the fuel gases and generate a hot combustedproduct gas that can be contacted directly with the gypsum feed tocalcine the gypsum and drive off the chemically bound water and formstucco. The contacting of the hot gases and the gypsum can be performedin an impact mill, where both calcination and grinding is performed.Alternately the hot gases can be used to transfer the heat to the gypsumin a kettle calciner where the heat is transferred to the gypsum in anindirect manner.

To modulate the temperature of the hot gases contacting the gypsum inthe calciner, a recycle fan (126 a) may be used to re-circulate coldexhaust gases from the calciner (122 a) exit to the front of thecalciner or the burner (112 e) as shown in FIG. 6.

In addition to the above, another portion of the hot combustible productgas from the activated carbon production reactor can be directed to aboiler (112 c) or hot oil heater (112 b) and combusted to generate hotcombusted gas (FIG. 4). In either of these devices, steam or “hot” oilis produced by transferring the heat from the combustion gases toprocess fluid. The “hot” steam and/or “hot” oil is directed to the boarddryer (124), where the heat transferred to gases that are used to drythe wallboard. The steam and/or the “hot oil” act as a heat transferfluid. In this manner, a clean gas stream can be used to dry thewallboard and contact with the “dirty” gases from the combustion of thehot combustible product gas from the activated carbon production reactoris prevented.

Process Control for Wallboard Manufacturing

In another embodiment, natural gas is used in combination with thecombustible product gases from the activated carbon production reactorto enable control of the temperature of the hot gas mixture. Theproportion of natural gas can be minimized and set at values justnecessary for process control.

Co-firing of natural gas and activated combustible product gas from theactivated carbon production reactor also enables “assured” processoperation or back-up fuel in case the activated carbon productionreactor (ACPR) has to be shut down.

Several exhaust gas streams in wallboard production are almost puresteam (moisture). For example, if an indirect kettle calciner is usedfor the production of stucco, the exhaust gases from the calciner isalmost completely pure water vapor. This stream may be advantageouslyused as process gas for the activation step in the activated carbonproduction reactor.

Similar to the previous embodiment of the co-production of activatedcarbon and ethanol, the following advantageous aspects are included inthe preferred embodiments of co-production of activated carbon andgypsum wallboard.

(i) Cooling of hot activated carbon product with moisture-rich gasesfrom wallboard manufacturing

(ii) Use of moisture-rich exhaust gases from the wallboard manufacturingas process feed gas for carbon activation in the activated carbonproduction reactor

Removal of SO₂ Generated from the Combustion of Product Gas from theActivated Carbon Production Reactor

In another embodiment of the invention, if the combined activated carbonand wallboard plant is located at a coal-fired power plant equipped witha wet flue gas desulfurization scrubber making gypsum for supply to thewallboard plant, the lime/limestone slurry from the coal-fired plant'sscrubber system may be advantageously pumped via pipe-line to thewallboard production section of the co-production plant. A wet scrubbersystem may be employed to remove SO₂ from the process gases generatedfrom the combustion of the hydrogen-rich product gas from the activatedcarbon production reactor using the lime/limestone slurry from thecoal-fired power plant. The “used-up” slurry can be returned to thecoal-fired plant wet scrubber system for additional processing (forexample, oxidation to gypsum and separation). In this manner, capitalequipment required for scrubbing SO₂ from the gases generated from thecombustion of product gases can be minimized as the feed lime/limestonepreparation and “used scrubber liquid” handling can be performed in anefficient manner with the coal-fired scrubber system.

EXAMPLES Example 7 Integrated Wallboard and Activated Carbon ProductionPlant

An integrated wallboard and activated carbon production plant with theidentified improvements (FIGS. 4, 5 and 6) and advantages relative tostand-alone plants is described below.

Coal (lignite) of the composition identified in previous examples isused as feed stock. The production of process heat for drying the raw“wet” gypsum feed section of the process is performed in the followingmanner (FIG. 5). About 5000 kg/hour of coal is introduced into amultiple hearth furnace. About 8000 kg/hour air and 3500 kg/hour steamis introduced in the various hearths of the MHF to generate the heatrequired and provide the optimum gaseous environment for the productionof activated carbon. About 1000 kg/hour of activated carbon is producedfrom this reactor set-up. The hot combustible product gases leaving themultiple hearth furnace (activated carbon production reactor) at the topis sent to the gypsum dryer burner in the wallboard plant. Additionalair is added to the burner (Air-2-7300 kg/hour) to completely combustthe hydrocarbons to yield an approximately 1900° C. hot gas. This ismixed with the cold exhaust to generate process hot gas of at about78,700 kg/hour at 530° C. The amount of heat supplied by this hot gas issufficient to dry 124 short tons per hour of approximately 10% moistureraw gypsum feed.

The production of process heat for the gypsum calcining section isperformed in the following manner (FIG. 6). An additional of about 6550kg/hour of coal is introduced into the multiple hearth furnace alongwith about 10000 kg/hour air and 4600 kg/hour steam to produce anadditional 1350 kg/hour of activated carbon from this reactor set-up.The hot combustible product gases leaving the multiple hearth furnace atthe top is sent to the gypsum calciner burner in the wallboardproduction section of the co-production plant. Additional air is addedto the burner (Air-2-10000 kg/hour) to completely combust thehydrocarbons to yield an approximately 1900° C. hot gas. This is mixedwith the cold exhaust to generate process hot gas of at about 99,000kg/hour at 560° C. The amount of heat supplied by this hot gas issufficient to calcine 108 short tons per hour of dry gypsum feed toyield 91 short tons of stucco.

The activated carbon production reactor can be sized to provide enoughcombustible process gas for feed drying, calcination and board dryingsteps of wallboard production—and splitting the product gas to direct toeach end application.

IV. Co-Production of Activated Carbon and Cement:

Cement manufacturing generates about 2 tons of CO₂ for every ton ofcement clinker of produced. Half of the CO₂ produced is from thecombustion of the fuel required for the clinkering and calcinationprocess. There is a need to reduce CO₂ emissions from cement clinkermanufacturing.

In this embodiment (FIG. 7), activated carbon and cement/lime isco-produced in the co-production plant (140). The combustible productgases from the activated carbon production reactor (26) from theactivated carbon manufacturing section of the plant (20) are directed tothe cement manufacturing section of the plant (150). There, thecombustible gases are advantageously combusted in either the cementclinkering kiln or in the pre-calciner section (154) (FIG. 7), with theenergy used to calcine limestone (CaCO₃) to lime (CaO). The combustiblegases are advantageously combusted in a burner (152) prior to or whilecontacting the limestone. In this manner, a lower carbon/hydrogen ratiofuel is used for process heat compared to the entire coal thus reducingthe overall CO₂ emissions from cement/lime manufacturing section (150).Again, as described in previous embodiments, the carbon-dioxide richflue gases from cement manufacturing may be used as reaction process gasin the activation section of the activated carbon production reactor. Ifsteam is required for activation instead of carbon dioxide, then aportion of the energy in the hydrogen-rich combustible gases may beadvantageously used for steam generation in a boiler (152), which may becombined with the hydrogen-rich combustible gas burner. The exhaust fromthe calciner is typically at high temperatures and is typically cooled(for example, by water quench) in the gas cooler (156) before it iscleaned and exhausted.

Example 8 Integrated Cement and Activated Carbon Plant

The energy content in the coal used is about 6400 Btu/lb and the totalenergy content coming into the process with the coal is 300 MMBtu/hr(21,220 kg/h or 46,680 lb/h coal). The energy content leaving theprocess with the activated carbon is about 99 MMBtu/hr. The remainder isabout 200 MMBtu/hr and is the energy content of the hydrogen-richcombustible gases. The amount of limestone calcined is 30,026 kg/h. Theamount of energy required for limestone calcination (heating to 800° C.and heat of calcination) is 75 MMBtu/hr which is about 38 percent of theenergy content of the hydrogen-rich (carbon-deficient) combustiblegases. The energy required for water evaporation for the process(activation) corresponds to about 14,854 kg/h (32,700 lb/h) or about 33MMBtu/hr. This corresponds to another 16 percent of energy utilizationor a total of about 50 percent utilization of the energy in thehydrogen-rich combustible gases. This process example has a lowerutilization efficiency compared to previous examples because the heatdelivery has to occur at a high process temperature (800° C. forcalcination).

Other embodiments of this invention may be accomplished in a method andsystem for co-producing a product (such as upgraded coal or biomass) inan energy consuming process and a carbon-rich product (such as activatedcarbon) from a hydrocarbon material such as coal or biomass. This isperformed by directing the hydrogen-rich (carbon-deficient) combustiblegases from the activated carbon production reactor and using its energycontent by combusting it and using the released energy to a highefficiency in the energy consuming steps of manufacturing of theco-product.

These preferred embodiments are described below.

V. Activated Carbon and Upgraded/Dried Coal Co-Production (Single stageDrying)

Activated Carbon Production from Hydrocarbon Feedstock and Production ofLower C/H Ratio Hot Combustible Product Gas than Parent Feedstock

In this method (FIG. 8) activated carbon and an upgraded/dried coalproduct are produced in co-production plant (10). Activated carbon isproduced in the activated carbon manufacturing plant section (20) bycarbonizing a solid or partially solid (e.g. wet) carbonaceous materialto yield a carbonized product and carbonization product gases;activating the carbonized product with steam or carbon dioxide to yieldactivated carbon and activation product gases; such that the combinationof the carbonization product gases and the activation product gases(hydrogen-rich hot combustible product gases from the activated carbonreactor) have a lower carbon-to-hydrogen (C/H) ratio compared to theparent carbonaceous material. In the above method carbonizing orpyrolysis is typically performed at 400 to 600° C. and activation withsteam is performed at 700 to 1000° C.

Activated carbon produced by the above method has a surface area of atleast 200 m²/gm, preferably at least, 300 m²/gm, and more preferably atleast 400 m²/gm. Surface areas are determined by theBrunauer-Emmett-Teller N₂ adsorption method.

A multiple hearth furnace (MHF) may be used as the activated carbonproduction reactor (26). Coal or other carbonaceous feedstock isprepared via hammer mills (24) to about ⅛″ to ½″ in size and introducedto the top of the activated carbon production reactor. The carbonaceousmaterial goes through a series of steps including drying,devolatilization and activation in the MHF to product activated carbon.The hot gases leaving the activated carbon production reactor containfine particulate. The fine particulate, which is partially processedmaterial, is collected in a cyclone (28) and advantageously returned tothe reactor for further processing.

The hot gases leaving the activated carbon production reactor alsocontain condensable tar. In one embodiment of the process, the hot gasesare contacted with “dry” coal product (from the coal dryer section) incyclone (28) to lower the temperature of the gases and condense the taronto the coal particles. In another embodiment of the process, a secondcyclone or a contacting device may be disposed after cyclone (28) toperform the contacting. The proportion of “dry” coal (from the coaldrying section) used is expected to be a function of the amount of tarpresent in the fuel gas and it is preferred that the tar/“dry” coalratio is maintained less than about 5 percent to ensure a flowableproduct. For a 5000 kg/hr coal feed to the activated carbon reactor, andassuming a 5 percent conversion of coal to condensable tars (250 kg/h),one would need to contact the hot gases leaving the activated carbonproduction reactor with more than about 5000 kg/hr of “dry” coal fromthe coal drying section to result in a non-sticky flowable product. Inanother preferred embodiment, the hot gases leaving the activated carbonproduction reactor and containing tar are contacted with “wet” coal. Thesensible heat in the reactor exit gases can be beneficially used toevaporate the moisture in the coal, while simultaneously lowering thetemperature of the combustible gases and depositing and solidifying thetar on the coal. It is advantageous to cool the combustible gases to atemperature in the neighborhood of 300° F., to facilitate low powerrequirements for pumping and ease of handling. The “dried” coalgenerated in the above manner is then separated from the combustiblegases either in a cyclone or another particulate separation device. Theresulting combustible gases are cooled relative to their exit from theactivated carbon production reactor and are also stripped of their tarcontent. This facilitates and enables the transport of the combustiblegases over long ducts to other portions of the combined plant withoutthe risk of fouling of those ducts and tar buildup. This also providesgreater flexibility on the location where the combustible gases can becombusted for heat supply to the companion process. In other preferredembodiments, contacting with a combination of “dry” and wet coal/biomasscan also be used to lower the temperatures of the combustible gases fromthe activated carbon production reactor and to capture and solidify thetar.

Chemical activation of the carbonaceous feedstock instead of physicalactivation may also be used. In chemical activation, the carbonaceousmaterial is mixed with a dehydrating agent such as zinc chloride,phosphoric acid or alkali hydroxide such as potassium hydroxide. This isfollowed by heat treatment to temperatures between 450 and 900° C. tocarbonize the material and release hot combustible product gases.

Activated carbon made by the above method can be further processed inthe carbon treatment unit (30) by grinding to a fine powder to less than30 microns in mean particle size and preferably to less than 10 micronsin mean particle size. The activated carbon made by the above method mayalso, in addition, be impregnated with halogens such as bromine orbromine compounds, such as ammonium bromide, to form enhanced activatedcarbon. Such enhanced activated carbon is advantageously used assorbents for mercury removal from coal-fired power plant flue gases asis well known in the art.

In this first embodiment, the co-product manufactured through one ormore energy consuming steps is an upgraded/dried coal. In the coaldrying section (50) of the process (FIG. 8), raw wet coal is firstcrushed to an appropriate size (typically less than 1 inch) in crusher(130) and fed to a coal drying reactor or chamber (120). The dried coalproduct from the coal dryer may be further compacted in a dry materialcompaction device (170) for purposes of improving the transporting andhandling characteristics of the dry coal product. The compaction deviceis one known in the art, where high pressures are used to collapse thepores within the coal matrix, thus preventing infiltration of air andoxidation during storage and handling.

Alternately, the raw wet coal is first crushed to an appropriate size(typically less than 1 inch) in crusher (130) and fed to a compactiondevice (140) and the wet briquette fed to the coal dryer (120). Thecompaction device can be a roll press, where the material passes betweentwo rollers spaced only a short distance apart relative to the inputcoal size. Compaction pressures of at least 5000 psi and up to 100,000psi may be used to compress the wet coal, collapse the pores within thecoal matrix and “squeeze” out the water trapped within the pores. Thecompaction step may be repeated several times to remove additionalmoisture within the coal matrix. The resulting products are a “drier”coal and squeezed out water. The compacted and dried coal may be used asa “dry” product (not shown) as is or further dried to remove the surfacemoisture in a coal dryer (120). The water stream from the compactiondevice (140) may contain some organics from the coal as well as someinorganic impurities. The water stream can be cleaned with methods knownin the art of wastewater treatment. In one embodiment, the watertreatment step includes mixing it with activated carbon and separatingthe activated carbon or passing it through an activated carbon bed (150)to remove organic and other impurities. The spent activated carbon canbe advantageously recycled to the activated carbon reactor (26).

Production of Hot Combusted Gas for Wet Coal Drying from the Combustionof Combustible Product Gas from the Activated Carbon Production Plant

In this embodiment of the inventive process, activated carbon and drycoal product are co-produced in a plant (FIG. 8), and at least a portionof the process heat required for the coal drying section of the plant isproduced through the combustion of hydrogen-rich combustible gasgenerated in the activated carbon production reactor. Theburner/combustor (112) is one known in the art and typically comprises aburner and combustion chamber. The hot combusted gases may beattemperated by mixing with cold air or with recycled cold exhaust gasfrom the drying plant section before being used in the coal dryer.

The coal dryer (120) can one of many types that are known in the art.The coal dryer can be a direct contact dryer, where the wet crushed coalor wet briquettes are contacted directly with the hot combusted orattemperated gases from the burner/combustor (112)—see FIG. 8. Thedirect contact dryer could be a flash drier, where the “wet” coalparticles or crushed briquettes are entrained with the hot gases,evaporating the water/moisture associated with the coal and transferringit to the gaseous phase. The dried coal is then separated in a firstparticulate separation device consisting of a cyclone or multiplecyclones and the exhaust gases from the first particulate separationdevice cleaned further in a second particulate removal device such asbag-house or electrostatic precipitator. The second particulate removaldevice may be combined with a dry scrubber with lime injection for SO₂control and/or activated carbon injection for mercury removal from theexhaust gases as is known in the art. Alternately, the direct contactcoal dryer could be rotary kiln where the wet coal/briquette size isrelatively large and the velocities in the kiln are relatively low suchthat the dried coal is not entrained and is removed via gravity at thekiln exit. The exhaust gases, along with the evaporated moisture, arecleaned as described in the aforementioned fashion, for example with abag-house.

Alternatively, the coal dryer can be indirect contact dryer. In thiscase, the hydrogen-rich combustible gases from the activated carbonreactor can be directed to a burner-combustor-boiler (steam generatingunit), where the sensible and chemical energy in the combustible productgases from the activated carbon production is converted by reacting withair (combustion), and the hot gases generated from combustion used tomake steam at a temperature and pressure that would be adequate forutilization in the energy consuming steps of coal drying. Alternatively,or in addition, combustible gases can be directed to a furnace [e.g.,heat transfer fluid (oil) heating unit)] where the sensible and chemicalenergy in the product gases from the activated carbon production isconverted to heating a “non-contact heat transfer fluid” that would beadequate for utilization in the energy consuming steps of coal drying.In both of the above cases, the steam/“hot” oil is used to transfer itsenergy to the wet parent hydrocarbon feed indirectly to evaporate themoisture in the parent hydrocarbon and generate a “dried” hydrocarbonmaterial that has a higher energy content per unit mass. The indirectcoal dryer can be a rotary kiln with a shell that is heated with thesteam or the “hot” oil. Alternately, the indirect coal dryer could be afluidized bed embedded with steam coal or “hot” oil coils. Wet coalwould be fed to the fluidized bed and the heat in the steam/“hot” oiltransferred through the tube walls to the coal to drive off themoisture. Methods well understood in the art can be used to separate theevaporated moisture from the dried coal.

In all of the above cases, the flue gas generated from the combustion ofactivated carbon reactor product gases has a lower CO₂ content per unitof heat generated than direct combustion of the feed coal or biomass.

Cooling of Hot Activated Carbon Product with Moisture-Rich Gases fromCoal Dryer Section

Activated carbon leaving the bottom of the activated carbon productionreactor, such as a MHF is at a high temperature, typically around 1500to 1700° F. This hot material is typically cooled with an indirect heatexchanger before being discharged. In an embodiment of the invention,the hot activated carbon product is advantageously cooled withmoisture-rich gas stream from the coal dryer section of the plant, inparticular the clean exhaust leaving the bag-house/carbon (160) bed ofthe coal dryer section, in a heat exchanger (not shown). The heatexchanger can be of an indirect contact type, or a direct contact heatexchanger. If direct contact heat exchange is used, the gas streamsshould have a maximum of about 1 percent O₂, preferably less than 0.5%O₂ to prevent oxidation and degradation of the activated carbon product.The heat exchanger is preferably operated in a predominantlycounter-current mode, with the hot activated carbon product and the“cooling” gas streams flowing in a counter-current fashion. The heated(moisture-rich) gas stream can then be advantageously used subsequentlyas process gas in the activation step of the activated carbon plant.

Use of Moisture-Rich Exhaust Gases from the Coal Dryer Section of the asProcess Feed Gas for Activation in the Activated Carbon ProductionReactor

In another embodiment of the combined activated carbon and coal dryingplant, at least a portion of the exhaust gas streams in the coal dryingsection of the plant that has very high moisture content is used asactivation process gas. For example, if an indirect steam-driven dryeris used for the drying process, the exhaust gases from the dryer (fromthe drying process) are almost completely pure water vapor. This streammay be advantageously used as process gas for the activation step in theactivated carbon plant. This gas stream may be advantageously preheatedas described in the preceding paragraphs before introduction into theactivation section of the activated carbon plant. By using themoisture-rich stream from the coal drying section in the activatedcarbon plant, water and energy consumption for the combined plant isreduced, since steam required for the activation step in the activatedcarbon plant does not have be raised separately.

The flue gas from the combustion of the hydrogen-rich (carbon-deficient)combustible gas produced by the activated carbon reactor is treated toreduce the concentration of various pollutants in a manner that is knownin the art. For example, ammonia can be injected in the flue gases at atemperature of about 1500-1800° F. to reduce the nitrogen oxides tomolecular nitrogen. Alkaline material, such as lime slurry can beinjected into the flue gas after it has been used for drying and itstemperature lowered to capture sulfur oxides, and the coal ash andscrubber particulate can be removed using a dust collector such as afabric filter (160).

Use of “Dry” Coal Product as Feed for the Activated Carbon ProductionReactor

In an alternate embodiment, instead of wet coal as feed to the activatedcarbon manufacturing section (20), a drier coal is used as feed. In oneembodiment, a portion of the dry coal product from the wet feed coaldryer (120) in the coal drying section (50) is routed to the grinder(24) in the activated carbon manufacturing section. In anotherembodiment, a portion of the dry compacted coal product from the drycompactor (170) is routed to the grinder (24). In yet anotherembodiment, a portion of the partially dewatered briquette from thecompaction device (140) is routed to the grinder (24) and as feed to theactivated carbon reactor (26). In all of the above cases, the use of adry feed to the activated carbon production section results in less heatduty requirements in that section and a higher production throughput ofactivated carbon product for a given size reactor (26).

Co-Firing of Coal and Hot Combustible Product Gas from the ActivatedCarbon Production Plant for Coal Drying

In an alternate embodiment, if the coal drying section of the plantrequires more energy than what is provided by the combustion of thehydrogen-rich combustible gas from the activated carbon reactor,supplemental firing of additional fuel may be used. This additional fuelcan be coal, preferably, or an alternate fuel, such as natural gas.

The hydrogen-rich combustible gas from the activated carbon productionreactor may be fired simultaneously with the supplemental fuel in anadvantageous manner to reduce pollutant emissions such nitrogen oxides.For example, the hydrogen-rich combustible gas may be preferentiallyintroduced in a reducing zone of the combustor, followed by stagedaddition of combustion air into the combustor to minimize nitrogen oxideformation and complete combustion. Alternately, the combustible productgas can be introduced into the combustor as a “re-burn” fuel at adownstream location of the combustor to reduce nitrogen oxides formedupstream in the combustor.

Boosting Pressure of the Hot Combustible Product Gas from the ActivatedCarbon Plant

Depending on the operation of the activated carbon reactor, thehydrogen-rich combustible gas from the reactor may need to be deliveredat a higher pressure to downstream components/devices than madeavailable at the exit of the reactor. A higher pressure may be required,for example, to obtain better distribution of the combustible gas withina downstream device. In such cases, a fan (40) that can handle hot andparticulate-laden gas streams may be used. If the combustible gas fromthe activated carbon plant has too high a temperature for it to beeffectively handled by a fan, then it may be cooled down to thenecessary temperature before its introduction into the fan. Cooling maybe achieved with a heat exchanger or by mixing in a cold gas stream.

Destruction of Volatile Organic Compounds in Exhaust Streams from CoalDrying Section in the Activated Carbon Production Plant or theBurner/Combustor

The coal dryer section may emit volatile organic compounds (VOC). Toprevent emission of VOC into the environment, these streams may beadvantageously routed to the bag-house/carbon bed (160), where theorganic compounds may be captured by the carbon. The spent carbon may berecycled to the activated carbon reactor (26) or the burner/combustor(112) for VOC destruction.

Removal of Condensable Tars from the Activated Carbon Reactor ProductGases

The devolatilization of coal releases tars that are carried out of theactivated carbon production reactor with the combustible gases. Thesesgases have to be maintained at a relatively high temperature to preventcondensation of the tars and equipment fouling. It also requires thatthe burner/combustor for oxidizing the combustible gases be physicallyclosely coupled to the activated carbon production reactor. In apreferred embodiment, the dry coal product from coal dryer (120) (seeFIG. 8) is mixed with the combustible gases in a mixing and separationdevice such as cyclone (28) or in a cyclone or other mixing devicedownstream of the cyclone (28). The combustible gases are advantageouslycleaned of their tar content, allowing for their transport and handlingwithout the risk of downstream equipment fouling. The dry coal productis also enhanced as it covered with hydrophobic tar material making itless susceptible to oxidation and wetting.

In another preferred embodiment, the hot gases leaving the activatedcarbon production reactor and containing tar are contacted with “wet”coal. The sensible heat in the reactor exit gases can be beneficiallyused to evaporate the moisture in the coal, while simultaneouslylowering the temperature of the combustible gases and depositing andsolidifying the tar on the coal. The “dried” coal generated in the abovemanner is then separated from the combustible gases either in a cycloneor another particulate separation device. The resulting combustiblegases are cooled relative to their exit from the activated carbonproduction reactor and are also stripped of their tar content. Thisfacilitates and enables the transport of the combustible gases over longducts to other portions of the combined plant without the risk offouling of those ducts.

EXAMPLES Example 9 Thermal/Flash Drying of Wet Coal to Produce “Dry”Coal and Activated Carbon Production

An activated carbon production and “dry” coal production (using athermal/flash drier) plant with the identified improvements (FIG. 9) andadvantages relative to stand-alone plants are described below.

Coal (lignite) of the composition provided below is used as feed stockfor activated carbon.

Composition wt-% C Carbon 34.6 H Hydrogen 3.5 S Sulfur 0.61 O Oxygen21.6 N Nitrogen 0.66 Ash 7.0 H₂O Moisture 32.0

Activated carbon is produced in the activated carbon manufacturingsection (20 a). Yield from the activated carbon production reactor (26a) is about 20-30 percent based on wet feed input. For a 5,000 kg/hourwet lignite input, this plant yields about 1,025 kg//hour (20 percentyield) of activated carbon product.

A typical activated carbon composition is shown below obtained fromprocessing the above-described feed stock in the proposed inventivemethod.

Composition wt-% C Carbon 68 H Hydrogen 0.5 S Sulfur 1.5 O Oxygen 0.5 NNitrogen 0.7 Ash 28.0 H₂O Moisture 1.0The elemental composition of the combustible gases prior to any partialoxidation or steam reforming is given below:

Composition wt-% C Carbon 26.3 H Hydrogen 4.3 S Sulfur 0.4 O Oxygen 26.9N Nitrogen 0.7 Ash 1.8 H₂O Moisture 40.0The heating value of the wet coal (lignite) with the compositionprovided above is about 14.8 MJ/kg on a lower heating value basis. TheCO₂ emissions from the combustion of 1 kg of coal is calculated to be1.27 kg, thus resulting in 11.7 MJ of heat released per kg of CO₂emitted. In contrast, the heating value of the combustible gases (priorto composition and energy changes from partial oxidation or steamreforming in the activated carbon production reactor) is estimated to be12.8 MJ/kg on a lower heating value basis. The CO₂ emission from thecombustion of these gases is calculated to be 0.96 kg, resulting in 13.3MJ of heat released per kg of CO₂ emitted. The combustible gasesrepresent a less CO₂-polluting fuel stream compared to the parent coal.

In addition to activated carbon, the activated carbon reactor produceshydrogen-rich combustible product gas which is sent to the coal dryingsection (110 a) of the co-production plant (100 a). A higher moisture(38 weight % H₂O) coal is used as feed stock for the coal drying section(110 a) in the proposed inventive method. Wet coal is fed to the coaldryer (120 a). The “dry” coal product from the dryer has a lowermoisture content compared to the wet coal feed. 51,000 kg/hour of wetcoal having a moisture content of 38 weight percent is dried using theheat from combusting the hydrogen-rich syngas from the activated carbonreactor to generate a 36,345 kg/hour of “dry” coal product having amoisture content of 13 weight percent. Based on the moisture content ofthe raw coal and “dry” product, about 1.4 kg of raw wet coal is requiredto produce 1.0 kg of “dry” coal product in this example.

Steam requirement for activation for the activated carbon productionplant is about 0.7 kg of steam per kilogram of wet feed. For a 5,000kg/hour wet lignite input, this translates to about 3,500 kg/hour ofsteam. In addition to predominantly providing the heat for coal drying,in this example, a small portion of the energy from the combustion ofthe hydrogen-rich combustible product gas from the activated carbonreactor is also used to generate steam for the activation process. Thesteam generating unit, i.e. boiler (not shown) is attached to theburner/combustor unit 112 a and generates steam for the activated carbonreactor (26 a).

The hot combusted gas from the burner/combustor/boiler (112 a) has avery high temperature. It is attemperated advantageously with recycledexhaust from the wet coal dryer/bag-house (120 a). Recycle fan (126) isused to transport the cool exhaust gas to mix with the hot combusted gasfrom the burner/combustor (112 a). In this example, about 45,710 kg/hourof 120° C. exhaust gas is re-circulated to mix with hot combusted gas togenerate 68,470 kg/hour of attemperated hot gas as feed to the coaldrying unit (120 a).

The flue gas generated from the combustion of activated carbon reactorproduct gases has a lower CO₂ content per unit of heat generated thandirect combustion of the feed coal or biomass. For example, in the aboveexample 3,803 kg/hour of CO₂ with a CO₂ content of 5.13 volume percentin the exhaust gas is generated for the required amount of steam for theactivated carbon production and hot gases for coal drying. This comparesto 3,867 kg/hour of CO₂ (6.21 volume percent in exhaust gases) withdirect coal combustion is used for coal drying (see comparative Example12 below).

The energy content in the coal used is about 6400 Btu/lb and the totalenergy content coming into the process with the coal is (5000 kg/hr or11,000 lb/hour-70.4 MMBtu/hr. The energy content leaving the processwith the activated carbon is about 22 MMBtu/hr. The remainder, excludingheat loss to the environment, is about 48 MMBtu/hr and is the energycontent of the hydrogen-rich combustible gases. The energy used to drythe coal and evaporate the steam for the activated carbon reactor (3,500kg/hour) is about 40 MMBtu/hr. The efficiency of energy utilization isabout 83 percent.

The total amount of coal used for an integrated coal drying andactivated carbon plant is 5,000 kg/hour to the carbon production reactorand 51,000 kg/hour to the coal dryer. This produces 36,345 kg/hour of“dry” coal product and 1025 kg/hour of activated carbon product. Incomparison, a separately located coal-fired coal dryer and a coal-fedactivated carbon plant with flue gas quench would require a total of5000 kg/hour for carbon production and 3,050 kg/hour of coal to be burntfor drying the coal. The total CO₂ emissions from separately locatedplants would be 7,670 kg of CO₂/hour compared to 3,803 kg of CO₂/hourfor an integrated plant. Even if the separate activated carbonproduction plant is equipped with recovering the excess heat andconverting it to electricity, the efficiency of conversion is only about20 to 25 percent (Example 13) compared to about 83 percent for theintegrated coal drying-activated carbon plant.

Example 10 Co-Production of Activated Carbon and “Dry” Coal Using WetCoal Compaction Followed by Briquette Drying

An activated carbon production and “dry” coal production (usingcompaction followed briquette drying) plant with the identifiedimprovements (FIG. 10) and advantages relative to stand-alone plants aredescribed below.

Coal (lignite) of the composition provided in Example 9 is used as feedstock for activated carbon. A higher moisture (38 weight % H₂O) coal,similar to Example 9, is used as feed stock for the coal drying section(110 b) in the proposed inventive method (FIG. 10). In this method, thecompaction step reduces the moisture content of the coal from 38 percentto 28 percent in the compaction device. Consequently, a lower initialmoisture content coal briquette is fed to the coal dryer (120 b) fromthe compaction device (140 b). If the amount of energy transferred inthe hydrogen-rich combustible syngas from the activated carbonmanufacturing section (20 b) is the same as in Example 9, a largerquantity of partially dewatered coal briquettes can be dried to thefinal moisture content of the dry coal product as in Example 9.

In this case, the corresponding flows that satisfy the overall energybalance are 92,900 kg/hour of wet coal feed to the compaction device(140 b) resulting in 80,000 kg/hour of material with a moisture contentof 28 weight percent, which when fed to the coal dryer (120 b) produces66,210 kg/hour of dry coal product with a moisture content of 13 weightpercent. A higher throughput of dry coal product is achieved with thesame energy supply from the activated carbon production reactor comparedto Example 9 because only a portion of the moisture in the wet coal hasto be evaporated; the rest is removed as liquid water in the compactiondevice. The corresponding CO₂ emissions and energy efficiency areidentical to Example 9 and are dramatically improved in relation tocomparative examples (12, 13 and 14) described below.

Example 11 Co-Production of Activated Carbon and “Dry” Coal withThermal/Flash Drying and High-Moisture Gas Recycle to Activated CarbonFurnace

An activated carbon production and “dry” coal production (using thermaldrying only) plant (100 c) with recycle of high-moisture content gasfrom the exhaust of the dryer (120 c) to the activated carbon reactor(26 c) and other identified improvements (FIG. 11) and advantagesrelative to stand-alone plants are described below.

Coal (lignite) of the composition provided in Example 9 is used as feedstock for activated carbon. A higher moisture (38 weight % H₂O) coal,similar to Example 9, is used as feed stock for the coal drying section(110 c) in the proposed inventive method (FIG. 11). In this method, arecycle fan (180) takes a portion of the exhaust from the dryer (120 c),which has a high moisture content resulting from the evaporation ofwater from the wet coal in the dryer, and recycles it to the activatedcarbon manufacturing section (20 c). The high-moisture content recyclegas is used as steam for activation of the coal in the activated carbonreactor (26 c). If an indirect dryer is used, this stream would becompletely composed of water vapor. If a direct fired dryer is used, themoisture content of the gases is lower, but still relatively high. Thegas composition (volume percent) of the recycle stream is as shown belowfor a direct coal fired dryer in this example:

CO₂  5.3% H₂O 68.2% O₂  1.2% N₂ 25.3%Since the water vapor for the production of activated carbon is obtainedfrom the recycle gas and separate steam does not have to be generated inthe burner/combustor/boiler section (112 c) in this example, all of thechemical and thermal energy in the hydrogen-rich syngas from theactivated carbon production reactor can be used for drying in the coaldryer (120 c). Consequently a larger quantity of moisture can beevaporated in the coal dryer (120 c) compared to the dryer (120 a) inExample 9. In this case, the wet coal feed rate to the dryer is 60,000kg/hour and dry coal product rate is 42,760 kg/hour. This is higher thanthe product rate from the dryer (120 a) in Example 9, which is 36,345kg/hour. The corresponding CO₂ emissions and energy efficiency areidentical to Example 9 and are dramatically improved in relation tocomparative examples (12, 13 and 14) described below.

COMPARATIVE EXAMPLES Example 12 Separate Coal-Fired Boiler for CoalDrying

A typical coal-fired system necessary for providing the energy for coaldrying as in the integrated example is estimated to require 3,050kg/hour of coal firing. The coal considered in this case is a lignitecoal as described in the example with the integrated plant. Combustionof the above indicated quantity of coal will generate about 17,710kg/hour of flue gas, if the excess air used is about 20 percent abovethe stoichiometric requirement. Corresponding quantity of CO₂ emissionsin the flue gas is about 3,867 kg/hour, which is higher than the CO₂emissions (3803 kg/hour) obtained from firing the hydrogen-rich syngasfrom the activated carbon reactor. Additionally, no activated carbonproduct is produced in this example in contrast to Examples 9, and 11

Example 13 Coal-Fired Activated Carbon Plant with Flue Gas Quench

An example of a typical coal-fired activated carbon production plant isprovided below. Lignite of the composition provided in the previousexample is used as feed stock. Activated carbon yield is about 20percent based on wet feed input. A portion of the heat generated fromthe combustion of the product gases from the reactor is used to generateprocess steam. Steam requirement for the activated carbon productionplant is about 0.7 kg of steam per kilogram of wet feed. For a 5,000kg/hour wet lignite input, this translates to about 3,500 kg/hour ofsteam. This plant yields about 1,025 kg/hour of activated carbonproduct. The remainder of the heat from the combustion of the productgas from the activated carbon production reactor has to be quenched witha water spray. About 14,285 kg/hour of water is required to quench theflue gases and achieve an outlet flue gas temperature of about 300° F.,which is optimum for operation of the pollution control equipment. Thisprocess yields a CO₂ emission of about 3,803 lb/hour, but the energy inthe hydrogen-rich combustible gases is not utilized. No additional drycoal co-product is generated in this example in contrast to Examples 9,10 and 11.

Example 14 Coal-Fired Activated Carbon Plant with Heat Recovery forPower Generation

In a typical coal-fired activated carbon production plant flow diagramwith heat recovery for power generation, lignite of the compositionprovided in the previous examples is used as feed stock. Activatedcarbon yield is about 20 percent based on wet feed input. A portion ofthe heat generated from the combustion of the product gases from thereactor is used to generate process steam. Steam requirement for theactivated carbon production plant is about 0.7 kg of steam per kilogramof wet feed. For a 5,000 kg/hour wet lignite input, this translates toabout 3,500 kg/hour of steam. This plant yields about 1,025 lb/hour ofactivated carbon product. The remainder of the heat from the combustionof the product gas from the activated carbon production reactor iscooled, while additional steam is generated. This steam is sent to asteam turbine for electricity production. About 2.5 MWe of electricitycan be expected to be produced, with a heat-to-electricity conversion ofabout 20-25%. This process yields an overall CO₂ emission of about 3,803kg/hour.

Electricity generation using a steam turbine by itself, typically onlyhas energy efficiency utilization between 20 and 35 percent, but for aplant of this size closer to 20 percent. The remainder of the energy islost to the environment during steam condensation in the condenser,which is necessary to return water into a liquid state before it can becompressed and returned to the boiler. No additional dry coal co-productis generated in this example in contrast to Examples 9, 10 and 11, andthe efficiency of energy utilization of the combustible gases from theactivated carbon reactor is lower than 50 percent.

With respect to the above description then, it is to be realized thatthe optimum relationships for the elements of the invention, to includevariations in size, materials, shape, form, function and manner ofoperation, assembly and use, are deemed apparent to one skilled in theart, and all equivalent relationships to those illustrated in thedrawings and described in the specification are intended to beencompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed is:
 1. A method comprising: a) providing a parenthydrocarbon-rich solid material; b) activating the parent material byexposing it to a hot gas stream at atmospheric pressure, the gas streamresulting from partial oxidation of the parent material using air alongwith additional carbon dioxide and/or steam, to produce activated carbonwith a surface area of at least about 200 m²/gm, and a hydrogen-richcarbon-deficient combustible gas that has a lower carbon to hydrogenratio than the parent material; c) adding supplemental fuel to thecombustible gas and then combusting at least some of the combustible gasto produce heat; and d) using at least about 70% of the energy contentof the combustible gas to dry additional coal or biomass other than thatused in step a).
 2. The method of claim 1 further comprising: e)removing tars from the hot combustible gas stream before the gas streamis combusted by exposing the hot combustible gas to wet, cool, coal orbiomass before the combustible gas is combusted to therebysimultaneously condense the tars and dry the coal or biomass, wherein atleast a portion of coal or biomass dried in step d) is used to removetars from the hot combustible gas.
 3. The method of claim 1 furthercomprising using at least some of the heat to produce steam throughboiling water, and then using the steam in step b).
 4. The method ofclaim 3 wherein steam is raised before step d).
 5. The method of claim 1wherein CO2 emission per unit of heat produced in step c) of the methodis less than would have been generated by combusting coal to generatethe heat produced in step c) of the method.
 6. The method of claim 1wherein the coal or biomass is compacted before step d) to partially dryit.
 7. The method of claim 1 further comprising collecting water vaporcreated in step d) and using such water vapor in step b).
 8. The methodof claim 1 wherein coal or biomass drying results in the emission ofvolatile organic compounds (VOCs), wherein the at least some of the VOCsare combusted to produce heat and used in the step of activating theparent material.
 9. The method of claim 1 wherein the activated carbonhas a surface area of at least about 400 m²/gm.